This invention relates to a propeller for marine propulsion and more particularly to an improved, high strength, high efficiency propeller blade design.
As is well known, the function of a propeller in a marine propulsion unit is to drive the associated watercraft through the body of water in which it is operating. Normally, propellers for pleasure craft must be operated through a wide speed and load range and must have good efficiency throughout these running conditions. In order to prevent cavitation and to insure high efficiency, it has been has been the practice to provide a cup shaped depression in the trailing side of the forward face of the propeller blade. The rear or driving face of the blade is normally curved about an arc and the cup shaped depression on the front face prevents cavitation. However, in addition to providing good running efficiency, the propeller blade design should be such so as to insure high strength and long life. With the prior art type of constructions, this has necessitated the provision of a blade that is relatively wide in an axial direction. The use of such wide blades presents a number of disadvantages. In the first instance, the width of the blade causes an increase in resistance to turning and, accordingly, a loss of efficiency. Furthermore, as the width of the blade is increased, the likelihood of cavitation is still further increased.
It is, therefore, a principal object of this invention to provide an improved, high strength blade design for a marine propeller.
It is another object of this invention to provide a marine propeller blade design that insures good efficiency, high strength and resistance to cavitation and high efficiency.